Before anything else: they have to tell you why

A reviewable decision does not just arrive. Under subsection 100(1) the decision-maker must give written notice of the reviewable decision, and of the reasons for the reviewable decision, to each person directly affected by it. Reasons, in writing, are not a courtesy you request. They are part of making the decision.

The notice also has to tell you your options. Subsection 100(1A) requires a statement that the person may request a review of the reviewable decision in accordance with this section, or, for certain decisions, that the decision will be reviewed automatically, and that the person may seek further review under section 103.

Three months, and the clock starts when you receive the notice

Subsection 100(2) lets any person directly affected ask the decision-maker to review the decision. If you were given a notice, the person must make the request within 3 months after receiving the notice. Not three months from the decision. Three months from receiving the notice of it.

The provision almost nobody is told about

You do not have to write a letter. Subsection 100(3) allows the request to be made by sending or delivering something in writing, or by making an oral request, in person or by telephone or other means.

And the burden of recording it is not yours. If you ask orally, subsection 100(4) requires the person receiving the request to make a written record of the details of the request and to note on the record the day the request is made. So a phone call is a valid request, and the obligation to date it sits with the agency, not with you.

For anyone who finds written processes hard, which on this scheme is a great many people, that single subsection is the difference between a right that exists and a right that can be used.

The reviewer cannot be the person who decided

This is the second thing worth knowing. Subsection 100(5A) says the decision-maker cannot review the reviewable decision personally if the decision-maker was involved in making the reviewable decision, and 100(5B) extends the same bar to a delegate who was involved. Internal review is internal, but it is not the same desk.

What the reviewer may then do is set out in subsection 100(6), and it is all three options: confirming the reviewable decision; or (b) varying the reviewable decision; or (c) setting aside the reviewable decision and substituting a new decision.

Ninety days to decide

Subsection 100(6A) puts a clock on the agency as well. The reviewer must decide within a period set by the NDIS rules, or if there are no such rules, within the period of 90 days beginning on the day the request is received.

Note the structure, because it is the same shape we found in aged care: the Act sets the outer default and the rules can set the real number. If you are counting your own days, count from the source rather than from us.

Some decisions are reviewed without you asking

A small category is reviewed automatically. Where the decision-maker is taken to have made a decision because a statutory period ran out, under subsections 21(3), 47A(5) or 48(4), the notice must say the decision will be reviewed automatically. In other words, a decision the agency is deemed to have made by missing a deadline does not need you to challenge it.

That list grows on 1 October 2026. The Act that passed both Houses on 19 August adds subsection 47B(6) to it, which is the deemed refusal of a plan variation for a high support needs participant. It is one of three identical insertions that Act makes to section 100, the other two being into subparagraph 100(1A)(a)(ii) and subparagraph 100(6A)(b)(ii), and together they widen automatic review rather than narrowing anything.

If internal review does not fix it

Section 103 is the external step. Applications may be made to the Administrative Review Tribunal for review of a decision made by a reviewer under subsection 100(6). Note what that means in sequence: the Tribunal reviews the internal review decision, so the internal step is not optional decoration, it is the gateway.

An application may be made only by, or on behalf of, a person directly affected by the decision. The Tribunal is the Administrative Review Tribunal established by the Administrative Review Tribunal Act 2024, which replaced the Administrative Appeals Tribunal. Older guidance naming the AAT is describing a body that no longer exists under that name.

Our view

Labelled as opinion, on the provisions above. Section 100 is better drafted than its reputation. Written reasons by default, an oral request, a bar on self-review and a stated outer limit are real protections, and several of them are more generous than the equivalents elsewhere in Commonwealth administrative law.

The gap is not in the section, it is in what reaches people. The right to request a review by telephone, and the corresponding duty on the agency to write it down and date it, is the single most useful thing in the section for the participants least able to use a written process, and it is close to invisible outside the Act. It costs nothing to say. Any letter that tells someone they may seek a review could say, in the same breath, that a phone call counts.

What this page does not tell you

This describes the law, not your matter, and it is not legal advice. Whether a particular decision is a reviewable decision is decided by the table in section 99, which this page does not reproduce. We have not covered the separate complaints pathway to the NDIS Quality and Safeguards Commission, which is about provider conduct rather than agency decisions, and is a different route with different rules. Timeframes set by the NDIS rules can differ from the Act's default, so check the current rules before relying on the 90 days. The Act is quoted at the compilation stated in the dateline; it changes often, and one change to this section is already scheduled.